Greenstick Fracture of the Mandible in a Child

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To the Editor: The condyle is the most commonly injured area within the pediatric mandible is considered a primary growth center of the jaw in children. Direct trauma to the mandible can result in proximal transmission of force leading to injury of the condylar process.1 Lower subcondylar fracture associated with a greenstick fracture is usually seen in children above 6 years of age. Here, the authors report a typical example for greenstick fracture of mandible in a child and review current knowledge in the view this clinical picture. She was 7 years old and injured her mandible after falling onto her chin, as she was riding a bicycle. On physical examination, there was submandibular severe edema and ecchymosis (Fig. 1, bottom left). Her left upper incisive tooth was also fractured. Radiographic examinations showed that a linear fracture at the symphysis was associated with a continuation and separation of anterior and posterior cortex of the mandible toward to subcondylar region (Fig. 1, above left, middle). But there was no complete fracture at the subcondylar region (Fig. 1, above right). We considered this clinical picture as a greenstick fracture of the mandible. The treatment was open reduction and rigid fixation of the symphyseal fracture with 2 mini plates. There was no complication at the early follow-up period with good dental occlusion (Fig. 1, bottom right).
Greenstick fractures represent a transition between retained plastic deformation and complete cortical disruption; 80% of the tubular bone is cortical and its function is the mechanical stability. So cortex is more resistant to stress pressures. The bone probably failed initially as a greenstick injury and then subsequently failed completely splitting from inner and outer cortex. This is compatible with the splitting evident longitudinally in the patient. Germinal zone which chondroblast division is seen at a low rate appear to be weak areas into which fracture may propagate.2 Regarding special pattern of the fracture, ramus–condyle conjunction point deserves a close look. The condylar cartilage is a secondary cartilage which involves endochondral bone formation. It shows a special multidirectional capacity for remodeling in selective response to varied mandibular displacement in children.3 It is also pressure tolerant the adaptive requirements for the mandible. The condyle follows the growth of the whole ramus which is also an important anatomic part playing role in adaptive capacity of the condyle. During childhood development, the ramus becomes progressively more upright. Vertical lengthening of the ramus continue to take place after horizontal ramus growth cease and resorption occurs on the upper part of the posterior border. This remodeling change, when it takes place, may present a weak point at this developmental age of the mandible.
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